That is right, 4500G's master/slave stacking model wont support distributed link aggregation(DLA).
Since we are talking about servers, alternatively, you could bridge your two network cards(if we are talking Windows).
I believe gnu/Linux's bonding feature has an operational mode setting that wont rely on LACP and that is specifically used when there is no support from a switch. (its called balance-alb).
I can not predict what would happen if you used that mode on your stack.
Either way, it wouldnt be seen by the stack as single logical unit. =-z